This invention relates generally to a sootblower device for directing a fluid spray against heat exchanger surfaces in large scale combustion devices for cleaning the surfaces, and particularly to such device having improvements in the construction and design of its structural chassis or frame assembly.
Devices generally known as sootblowers are used to clean internal surfaces within boilers, furnaces, or other devices in which a fossil fuel is combusted. Sootblowers typically employ water, steam, air, or a combination thereof as a blowing medium which is directed through one or more nozzles against encrustations of slag, ash, scale, and/or other fouling materials which become deposited on the surfaces.
Typical sootblowers of the long retracting type have a retractable lance tube which is periodically advanced into and withdrawn from the combustion device and is simultaneously rotated such that one or more nozzles at the end of the lance tube project blowing medium jets tracing helical paths.
Conventional sootblowers of the long retracting type use an elongated chassis or frame assembly in which a carriage assembly is driven for movement along the frame. The lance tube is carried by and moved by the carriage. An internal drive mechanism within the carriage causes a drive pinion gear to rotate which meshes with an elongated toothed rack fixed to the frame, driving the carriage for longitudinal motion. Through another set of internal gears of the carriage, the lance tube is caused to rotate as the carriage and lance move longitudinally along the frame. Examples of such sootblower devices include the well known “IK” type sootblower manufactured by the Assignee which is described by U.S. Pat. Nos. 5,920,951 and 5,605,117, which are hereby incorporated by reference.
Manufacturers of sootblower devices are continuously striving to improve their performance and reduce their cost of production, operation, and maintenance. A significant cost factor in the production of a sootblower is the fabrication of its elongated frame. Generally speaking, a long retracting sootblower has a frame with two vertical side panels to which are welded or bolted parallel upper and lower tracks for the carriage to run along. The vertical sides are held apart either by an integral horizontal upper panel or, in the case of some sootblower devices such as Assignee's “IK 600” sootblower, by spacer bars or by cross-bracing. These sootblower frame side panels are typically sheet metal plates to which are connected an “L” shaped angle iron which provides the surface for running the carriage rollers and the toothed drive rack. Each of these components are separately manufactured, fabricated, shipped, and assembled to the frame. This fabrication is an expensive procedure requiring significant labor involvement and the need to fabricate and stock inventory.
The typical assembled sootblower frame requires a high degree of skill and precision in its assembly. The angle iron pieces which form the track surfaces must be accurately aligned and may become misaligned during use. The assembly requirements also mean that assembly operations are best performed at a centralized manufacturing site with specialized fixturing and labor, which limits flexibility in optimizing the supply chain. And finally, a typical sootblower frame is heavier and uses more material than a structurally optimized design.
Long retracting sootblowers require a frame assembly that is strong, stiff and geometrically true, and which allows the accuracy of alignment between the track surfaces for the carriage rollers and for mounting the toothed rack to be precisely maintained relative to each side of the frame. Further, it is difficult to maintain the accuracy of alignment (parallelism) between the surfaces of each rack and tracks.